Hybrid Turbulence Phase Screen Model Based on Position and Number Optimization of UOWC System

Underwater optical wireless communication (UOWC) is the primary technology that provides high-speed and low-latency area-intensive data interaction for the Internet of Underwater Things. The turbulence effect seriously affects the optical signal transmission, and establishing a comprehensive turbulence channel model is essential to improve the anti-turbulence capability of the UOWC system. In this article, a hybrid phase screen model based on the oceanic turbulence optical power spectrum inversion and the extended Zernike polynomials is proposed, which has sufficient frequency components and can better characterize the turbulence effect caused by the underwater changes in temperature and salinity. By optimizing the number and position of the hybrid turbulence phase screen, the root-mean-square error of the probability density function of the received light intensity between the simulation and the experimental measurement is only 1.8468 at a turbulence intensity of 0.1538. Finally, we demonstrate a hybrid quadrature amplitude modulation multipulse pulse-position modulation (QAM-MPPM) technique to improve the anti-turbulence performance of the UOWC system. The results show that under the same conditions, the UOWC system with a hybrid QAM-MPPM technique outperforms those with single QAM and MPPM modulation by 3 and 1 dB, respectively. The hybrid modulation technique also exhibits a better bit error rate and average outage probability performance under different turbulence intensities.